Polyolefin catalysts and method of preparing an olefin polymer

ABSTRACT

A method of manufacturing a polyolefin using a catalyst system of an ingredient (A) and ingredient (B), with ingredient A being obtained through successive reaction steps. Ingredient A is prepared by forming a mixture of (1) the combination of (a) metallic magnesium or an oxygen-containing organic compound of magnesium with (b) a mixture of a monohydroxylated organic compound and a polyhydroxylated organic compound, (2) oxygen-containing organic compounds of titanium and (3) at least one alpha-olefin having at least 4 carbon atoms, such as 1-hexene. The resulting solution is reacted in sequence with (4) at least one first halogenated aluminum compound, (5) at least one silicon compound and (6) at least one second halogenated aluminum compound. Ingredient B is an organometallic compound of metals from Group Ia, IIa, IIIa or IVa of the Periodic Table. The resulting free-flowing polyolefin is characterized by a large average particle size and small amount of fine particles.

This application is a division, of the application Ser. No. 596,141,filed Oct. 11, 1990 and now U.S. Pat. No. 5,135,995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a catalyst for a polyolefin system and amethod of preparing an olefin polymer using such catalyst.

2. Description of the Prior Art

The catalytic production of polyolefins, such as polyethylene, is wellknown. It is already known to use an inorganic or organic magnesiumcompound with a transition metal compound as a high activity catalyst.

In an attempt to prepare polymer particles having a low amount of fineparticles, it has been suggested in Japanese application 59-118120 filedJun. 11, 1984, published as application 60-262802 on Dec. 26, 1985, toutilize a catalyst system that includes a mixture of an ingredientobtained by the reaction of magnesium, titanium, organoaluminum, siliconand halogenated aluminum compounds in sequence, and a catalystingredient which is an organometallic compound.

More particularly, it is disclosed in the Japanese application that asolid catalyst ingredient A is prepared by having a homogeneous solutionof the combination of a metallic magnesium and a hydroxylated organiccompound (or an oxygen-containing organic compound of magnesium) and anoxygen-containing organic compound of titanium react in succession withat least one kind of organoaluminum compound, then at least one kind ofsilicon compound and then at least one kind of halogenated aluminumcompound. Catalyst ingredient A is mixed with an ingredient B which isat least one kind of an organometallic compound containing a metal fromGroup Ia, IIa, IIb, IIIa or IVa of the Periodic Table.

The reduction of the amount of fine particles of the polyolefin polymeris desirable for a number of reasons. The formation of deposits isinhibited during the polymerization reaction and during the processes ofseparation and drying of the polymer. Also, the scattering of fineparticles of polymer outside of the system is prevented. In addition,separation and filtration of the polymer slurry is much easier becauseof the narrow particle size distribution, and the drying efficiency isenhanced due to the improvement in fluidity. Furthermore. duringtransportation of the polymer, bridging does not occur in the conduitsor silos and problems with transferring the polymer are reduced.

Further, when the polymer is made by a multistage polymerization method,if the polymer has a wide particle size distribution, classification ofthe powder may occur in the reactor prior to transfer when the additivepackage is introduced and during the transportation stage after drying.Also, the quality of the polymer may be adversely affected since thephysical properties typically are different for different particlediameters.

In addition, it is desirable to provide a polymer which has a narrowmolecular weight distribution, as described in the Japanese application.This results in a polymer that has high impact strength.

Although it is stated in the Japanese application that excellent powdercharacteristics are obtained using the described type of catalystsystem, it has been found that such catalysts still produce excessiveamounts of polymer particles having a diameter less than 210 microns(referred to as fines) when used in a slurry reactor with an isobutanesolvent.

Commonly assigned U.S. patent application Ser. No. 422,469, filed Oct.17, 1989, and now U.S. Pat. No. 5,037,910, of the present inventorsdiscloses an improvement over the type of catalyst and polymer processdisclosed in the Japanese application. In such U.S. application, it isdisclosed that the presence of a polyhydroxylated organic compound, inaddition to the hydroxylated organic compound, significantly improvesthe particle size of the resultant olefin polymer and reduces the amountof fines. This is achieved while retaining the desirable properties ofnarrow molecular weight distribution and high catalyst activity

In the aforementioned U.S. patent application (the disclosure of whichis herein expressly incorporated by reference), it is also disclosedthat the addition of the halogenated aluminum compounds should takeplace at a temperature no higher than about 25° C. in order to reducethe amount of fines.

Although it has been found that the addition of the polyhydroxylatedorganic compound is highly effective in increasing the polymer particlesize and reducing the fines, nevertheless it would be desirable tofurther improve such catalyst in order to provide further enhancement inthe properties of the resultant olefin polymer. In particular, it wouldbe desirable to provide an improved catalyst system which increases theparticle size and decreases the amount of fines, while retaining thedesirable narrow molecular weight distribution and higher catalystactivity.

SUMMARY OF THE INVENTION

In accordance with this invention, there is provided a method forpreparing an olefin polymer, which method comprises polymerizing anolefin in the presence of a catalyst system comprising a combination ofingredients (A) and (B), wherein ingredient (A) is a solid catalystobtained by the reaction of a homogeneous solution comprising (1), (2)and (3) below:

(1) at least one of a mixture of (a) metallic magnesium and/or anoxygen-containing organic compound of magnesium and (b) the combinationof at least one monohydroxylated organic compound and at least onepolyhydroxylated organic compound in which each hydroxyl group isseparated by at least four atoms in the molecule; and

(2) at least one oxygen-containing organic compound of titanium; and

(3) at least one alpha-olefin having at least 4 carbon atoms; and inwhich said solution of (1), (2) and (3) is reacted in sequence with

(4) at least one first halogenated aluminum compound; then

(5) at least one silicon compound; then

(6) at least one second halogenated aluminum compound; and ingredient(B) is an organometallic compound containing a metal from Group Ia, IIa,IIb, IIIa or IVa of the Periodic Table.

Also in accordance with this invention, there is provided a catalystuseful for preparing an olefin polymer, the catalyst comprising acombination of ingredients (A) and (B), wherein ingredient (A) is asolid catalyst obtained by the reaction of a homogeneous solutioncomprising (1), (2) and (3) below:

(1) at least one of a mixture of (a) metallic magnesium and/or anoxygen-containing organic compound of magnesium and (b) the combinationof at least one monohydroxylated organic compound and at least onepolyhydroxylated organic compound in which each hydroxyl group isseparated by at least four atoms in the molecule; and

(2) at least one oxygen-containing organic compound of titanium; and

(3) at least one alpha-olefin having at least 4 carbon atoms; and inwhich said solution of (1), (2) and (3) is reacted in sequence with

(4) at least one first halogenated aluminum compound; then

(5) at least one silicon compound; then

(6) at least one second halogenated aluminum compound; and ingredient(B) is an organometallic compound containing a metal from Group Ia, IIa,IIb, IIIa or IVa of the Periodic Table.

It has been surprisingly found that the addition of an alpha-olefin tothe magnesium-titanium solution significantly increases the particlesize of the resultant olefin polymer and reduces the amount of fines. Inaddition, the polymer retains its desirable properties of narrowmolecular weight distribution and the catalyst is highly active.

While not wanting to be bound by any theory, it is believed that theaddition of the alpha-olefin to the magnesium-titanium solution promotesin-situ catalyst encapsulation or binding of the catalyst particlesduring the chlorination step.

The alpha-olefin may be added to the magnesium-titanium solution beforeor after it is heated to fuse. Preferably, the alpha-olefin is addedbefore the ageing step. Also, preferably the alpha-olefin is analpha-mono-olefin, most preferably hexene.

The catalysts of this invention are particularly useful in thepreparation of high density polyethylene using a loop reactor, attemperatures in the range of about 20° to about 110° C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The general preparation of the catalyst and the ingredients thereof aredisclosed in the aforementioned U.S. patent application, except for thealpha-olefin addition, and reference to such application is again made.

In the present invention, either metallic magnesium and/or anoxygen-containing organic compound of magnesium can be used as areactant to prepare the solid catalyst ingredient A. Metallic magnesiumis preferred, and may be in powder, particle, foil, ribbon or othershape.

As oxygen-containing compounds of magnesium, there may be employedmagnesium alkoxides, for example, methylate, ethylate, isopropylate,decanolate, methoxylethylate and cyclohexanolate, magnesium alkylalkoxides, for example, ethyl ethylate, magnesium hydroalkoxides, forexample, hydroxymethylate, magnesium phenoxides, for example, phenate,naphthenate, phenanthrenate and cresolate, magnesium carboxylates, forexample, acetate, stearate, benzoate, phenyl acetate, adipate, sebacate,phthalate, acrylate and oleate, oximates, for example, butyl oximate,dimethyl glyoximate and cyclohexyl oximate, salts of hydroxamic acid,salts of hydroxylamine, for example, N-nitroso-N-phenylhydroxylaminederivative, enolates, for example, acetylacetonate, magnesiumsilanolates, for example, triphenyl silanolate, and complex alkoxideswith magnesium and other metals, for example, Mg[Al(OC₂ H₅)₄ ]₂, and thelike. These oxygen-containing organomagnesium compounds may be usedindependently or as a mixture.

As the monohydroxylated organic compound used in combination with thepolyhydroxylated organic compound, there can be mentioned alcohols,organosilanols and phenols. As alcohols, alicyclic alcohols or aromaticalcohols having 1 to 18 carbon atoms can be used. For example, methanol,ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, n-hexanol,2-ethylhexanol, n-octanol, 2-octanol, n-stearyl alcohol, cyclopentanol,cyclohexanol, and the like can be mentioned. Organosilanols are thosewhich have one hydroxyl group and the organic group of which is selectedfrom the group of alkyl, cycloalkyl, arylalkyl, aryl, and alkylarylhaving 1 to 12 carbon atoms. Examples of such organosilanols aretrimethylsilanol, triethylsilanol, triphenylsilanol andt-butyldimethylsilanol. As phenols, phenol, cresol, xylenol, and thelike can be mentioned. The monohydroxylated organic compounds may beused independently or as a mixture of two or more. The presently mostpreferred monohydroxylated organic compound is n-butanol.

The polyhydroxylated organic compounds used in combination with themonohydroxylated organic compounds have their hydroxyl groups separatedby at least four atoms. These are preferably atoms of carbon, nitrogen,oxygen, silicon, sulfur or phosphorus, or any combination thereof. Suchcompounds may be dihydroxylated organic compounds, such as straight orbranched chain aliplatic diols, or alicyclic, heterocyclic or aromaticdiols. These diols may have their hydroxyl groups separated by 4 to 50atoms, more preferably 4 to 8 atoms. Examples of diols include1,4-butanediol, 1,6-hexanediol, 2,5-dimethyl-2,5-hexanediol, diethyleneglycol, 2,2'-thiodiethanol, n-ethyldiethanolamine, silanol terminatedpolydimethylsiloxanes and the like. Examples of the other classes ofdiols include 1,4-cyclohexanediol, dihydroxy-naphthalenes, quinizarin,2,4-dihydroxypyridine, and the like.

As other polyhydroxylated organic compounds, there can be mentionedaliphatic, alicyclic and aromatic polyalcohols. Examples are glycerine,pyrogallol, pentaerythritol and the like. The polyhydroxylated organiccompound may be used independently or two or more of such compounds maybe employed.

The presently preferred of such compounds are the aliphatic diols, of 4to 8 carbon atoms, particularly 1,4-butanediol.

The weight ratio of the polyhydroxylated organic compound to themonohydroxylated organic compound may vary. Preferably thepolyhydroxylated compound is present in an amount of about 25 to 75% byweight of the total weight of the monohydroxylated compound and thepolyhydroxylated compound, and more Preferably, about 25 to about 50% byweight. It has been found with certain compounds that if the amount ofthe polyhydroxylated compound is too high, an undesirable increase inthe viscosity of the mixture results.

When the solid catalyst ingredient (A) of the invention is made usingmetallic magnesium, it is preferable to add one or more substances whichcan react with metallic magnesium or form an addition compound with it,for example, polar substances such as iodine, mercuric chloride, alkylhalides, organic esters, organic acids and the like for the purpose ofpromoting the reaction.

As oxygen-containing organic compounds of titanium which are used withthe magnesium or oxygen-containing organomagnesium compounds, compoundsrepresented by a general formula [TiO_(a) (OR¹)_(b) ]_(m) may be used.R¹ represents a hydrocarbon group such as straight or branched chainalkyl group, cycloalkyl group, arylalkyl group, aryl group, alkylarylgroup or the like, having 1 to 20, preferably 1 to 10, carbon atoms; aand b (with a≧0 and b>0) are numbers compatible with the valency oftitanium, and m is an integer. It is desirable to use suchoxygen-containing organic compounds in which 0≦a≦1 and 1≦m≦6.

As specific examples, titanium tetraethoxide, titaniumtetra-n-propoxide, titanium tetra-i-propoxide, titanium tetra-n-butoxide(tetrabutyl titanate), hexa-i-propoxy dititanate and the like can bementioned. The use of oxygen-containing organic compounds having severaldifferent hydrocarbon groups may also be used. These oxygen-containingorganic compounds of titanium may be used independently or as a mixtureof two or more. The presently preferred titanium compound is tetrabutyltitanate.

The alpha-olefins which are added to the magnesium-titanium solutionhave at least 4 carbon atoms and preferably up to 18 carbon atoms. Ithas been found that alpha-olefins with less than 5 carbon atoms are ingeneral too volatile to be effectively added to the Mg-Ti solution. Thealpha-olefin may contain one or more olefin groups, includingalpha-mono-olefins, dienes and polyenes, and mixtures thereof, with thealpha-mono-olefins being preferred. The alpha-olefin may be linear orbranched. Examples of linear alpha-mono-olefins include 1-pentene,1-hexene, 1-octene, 1-decene, 1-dodecene, and 1-tetradecene, and thelike. Examples of branched alpha-mono- olefins include 3-methyl buteneand 4-methyl pentene and the like. Examples of dienes and polyenes thatmay be used include 1,4-hexadiene, 1,5,9-decatriene,2-methyl-1,7-octadiene, 1,6-octadiene, 1,9-decadiene,1,13-tetradecadiene and 2,6-dimethyl-1,5-heptadiene, and the like. Thepresently preferred alpha-olefins are 1-hexene, 1-octene and1-tetradecene, with the most presently preferred alpha-olefin being1-hexene. The alpha-olefin may be used individually or in combinationwith one or more other alpha-olefins. It has been found that withincreasing carbon atoms in the alpha-olefin, the polymer particle sizegenerally decreases and the amount of fines increases.

The alpha-olefin is preferably added to the Mg-Ti solution together witha hydrocarbon solvent to further dilute the solution. Such solventsinclude, for example, hexane, isobutane, cyclohexane, toluene and thelike.

The alpha-olefin is added in an amount which is effective to increasethe particle size of the resultant polymer and decrease the amount ofpolymer fines. Typically, the alpha-olefin is added in an amount ofabout 0.1 to about 1.0, more preferably about 0.25 to about 0.75 andmost preferably about 0.4 to about 0.6, mole of alpha-olefin per 100grams of Mg-Ti solution (undiluted, including the polyhydroxylatedcompound and the monohydroxylated compound).

Following the fusion reaction between the magnesium and titaniumcomponents, it is preferred to age the fusion product for a sufficientamount of time to improve the homogeniety of the mixture. Such heatageing may typically be at a temperature of about 45° C. to about 75° C.for about 1 to 2 hours.

As the first halogenated organoaluminum compounds which are thereactants described above in (4), there may be used compounds of theformula R_(n) ² AlY_(3-n), in which R² represents a hydrocarbon grouphaving 1 to 20 carbon atoms, preferably 1 to 8, Y represents a halogenatom, and n is a number such that 1≦n<3. R² is preferably selected fromstraight or branched chain alkyl, cycloalkyl, arylalkyl, aryl andalkylaryl groups. The halogenated organoaluminum compounds describedabove can be used alone or as a mixture of two or more compounds.

As specific examples of the halogenated organoaluminum compound, therecan be mentioned diethylaluminum chloride, ethylaluminum sesquichloride,i-butylaluminum dichloride, and the like. It is also possible to employaluminum compounds which form the desired compounds in situ, such as amixture of triethylaluminum and aluminum trichloride. The presentlypreferred compound is diethyaluminum chloride.

As silicon compounds which are the reactants described above in (5),polysiloxanes and silanes may be used.

As polysiloxanes, there can be used siloxane polymers which have achain, cyclic or three-dimensional structure and in the molecule ofwhich there are included at various ratios and with variousdistributions one or two or more of the repeating units represented by ageneral formula: ##STR1## In the formula, R³ and R⁴ independentlyrepresent atoms or residues capable of bonding to silicon, such ashydrocarbon groups of alkyl or aryl groups, having 1 to 12 carbon atoms,hydrogen, halogen, alkoxyl groups, allyloxyl groups, fatty acid residuehaving 1 to 12 carbon atoms, and the like. In the formula, p representsnormally an integer ranging from about 2 to about 10,000. However, allof R³ and R⁴ should not be hydrogen atoms or halogen atoms.

Specifically, there can be used as chain polysiloxanes,hexamethyldisiloxane, octamethyltrisiloxane, dimethylpolysiloxane,diethylpolysiloxane, methylethylpolysiloxane, methylhydropolysiloxane,ethylhydropolysiloxane, butylhydropolysiloxane, polymethylhydrogensiloxane, hexaphenyldisiloxane, octaphenyltrisiloxane,diphenylpolysiloxane, phenylhydropolysiloxane, methylphenylpolysiloxane,1,5-dichlorohexamethyltrisiloxane, 1,7-dichlorooctamethyltetrasiloxane,dimethoxylpolysiloxane, diethoxylpolysiloxane, diphenoxylpolysiloxaneand the like.

As cyclic polysiloxanes, there may be mentioned, for example,hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane,decamethylcyclopentasiloxane, 2,4,6-trimethylcyclotrisiloxane,2,4,6,8-tetramethylcyclotetrasiloxane,triphenyltrimethylcyclotrisiloxane,tetraphenyltetramethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane,octaphenylcyclotetrasiloxane, and the like.

As polysiloxanes having a three-dimentional structure, for example,those in which chain or cyclic polysiloxanes described above werearranged by heating, etc. so as to have a crosslinking structure can bementioned.

Such polysiloxanes preferably are in liquid state from a standpoint ofhandling and have a viscosity of about 1 to about 10,000 centistokes,preferably about 1 to about 1000 centistokes, at 25° C. However, theyare not necessarily confined to liquids and may be solid matters ascalled silicone grease collectively.

As silanes, silicon compounds represented by a general formula H_(q)Si_(r) R_(s) ⁵ X_(t) can be used. In the formula, R⁵ represents groupscapable of bonding to silicon such as alkyl, aryl, alkoxyl, andallyloxyl groups, fatty acid residues, etc., having 1 to 12 carbonatoms. The R⁵ groups may be of the same of different kinds; X representshalogen atoms which may be of the same or different kinds; q, s and tare integers not smaller than 0, and r is a natural number which isconnected with q, s and t such that q+s+t=2r+2.

As specific examples, there can be mentioned, for example,silahydrocarbons such as trimethylphenylsilane, allyltrimethylsilane,etc., chain and cyclic organosilanes such as hexamethyldisilane,octaphenylcyclotetrasilane, etc., organosilanes such as methylsilane,dimethylsilane, trimethylsilane, etc., halogenated silicons such assilicon tetrachloride, silicon tetrabromide, etc. alkyl- andaryl-halogenosilanes such as dimethyldichlorosilane,n-buyltrichlorosilane, diphenyldichlorosilane, triethylfluorosilane,dimethyldibromosilane, etc., alkoxylsilanes such astrimethylmethoxylsilane, dimethyldiethoxylsilane, tetramethoxylsilane,diphenyldiethoxylsilane, tetramethyldiethoxyldisilane,dimethyltetraethoxyl- disilane, etc., haloalkoxyl- and phenoxyl-silanessuch as dichlorodiethoxylsilane, dichlorodiphenoxyl- silane,tribromoethoxylsilane, etc., silane compounds containing fatty acidresidues such as trimethylacetoxysilane, diethyldiacetoxysilane,ethyltriacetoxysilane, etc., and the like.

The organosilicon compounds described above may be used independently oras a combination of two or more. The presently preferred compound ispolymethylhydrogen siloxane.

As the second halogenated aluminum compounds which are the reactantsdescribed above in (6), those represented by a general formula R_(z) ⁶AlX_(3-z) may be used. In this formula, R⁶ represents a hydrocarbongroup having 1 to 20 carbon atoms, preferably 1 to 8, X represents ahalogen atom, 3 and z represents a number such that 1≦z<3. R⁶ ispreferably selected from straight or branched chain alkyl, cycloalkyl,arylalkyl, aryl, and alkylaryl groups. These halogenated aluminumcompounds can be used independently or as a mixture of two or more. Thesecond halogenated compound(s) of (6) may be the same or different fromthe compound(s) of (4) above.

As specific examples of the second halogenated aluminum compounds, therecan be mentioned and for example, diethylaluminum chloride,ethylaluminum dichloride, i-butylaluminum dichloride, ethylaluminumsesquichloride and the like. It is also possible to employ aluminumcompounds which form the desired compounds in situ, such as a mixture oftriethylaluminum and aluminum trichloride and the like. The presentlypreferred compound is i-butyl- aluminum dichloride.

The solid catalyst ingredient (A) to be used in the invention can beprepared by allowing the reaction product obtained through the reactionbetween reactants (1), (2) and (3) to react in sequence with reactant(4), then reactant (5) and then reactant (6).

It is preferable to conduct these reactions in the liquid medium. Forthis reason, the reactions should be conducted in the presence of inertorganic solvents particularly when these reactants themselves are notliquid under the operating conditions or when the amounts of the liquidreactants are not ample. As the inert organic solvents, those which areconventionally used may be employed. Of these, aliphatic, alicyclic oraromatic hydrocarbons, halogenated derivatives thereof, or mixturesthereof can be mentioned. For example, isobutane, hexane, heptane,cyclohexane, benzene, toluene, xylene, monochlorobenzene and the likecan be used preferably.

The amounts of the reactants to be used in the invention are notparticularly confined, but the atomic ratio of gram atom of Mg in themagnesium compounds described above in (1) to gram atom of Ti in thetitanium compounds described above in (2) is preferably about0.05≦Mg/Ti≦200, preferably about 0.2≦Mg/Ti≦100. If the ratio of Mg/Ti istoo large out of this range, it becomes difficult to obtain ahomogeneous Mg-Ti solution at the time of the catalyst preparation orthe activity of catalyst becomes low at the time of the polymerization.Inversely, if it is too small, the activity of the catalyst also becomeslow resulting in the problems such as the discoloration of product, etc.

It is preferable to select the amount of organoaluminum compounds sothat the atomic ratio of gram atom of Al in the halogenated aluminumcompounds R_(n) ² AlY_(3-n) (with n being 1≦n<3) described above in (4),hereinafter referred to as Al (4), multiplied by n to gram atom of Ti inthe titanium compounds described above in (2) lies within the range of:##EQU1## is too large out of this range, the activity of the catalystbecomes low, and, if it is too small, a result is incurred that theimprovement in the powder characteristics cannot be achieved.

It is preferable to select the amount of silicon compounds so that theatomic ratio of gram atom of Mg in the magnesium compounds describedabove in (1) to gram atom of Si in the silicon compounds described abovein (5) lies within a range of about 0.05≦Mg/Si≦100, preferably about0.5≦Mg/Si≦10. If Mg/Si is too large out of this range, the improvementin the powder characteristics is insufficient. Inversely, if it is toosmall, the result is that the activity of the catalyst is low.

It is preferable to select the amount of the second halogenated aluminumcompounds described above in (6) so that the atomic ratio of gram atomof Al in the aforementioned first halogenated aluminum compounds (4)[Al(4)] to gram atom of Al in the second halogenated aluminum compounds(6) (hereinafter referred to as Al(6)) lies within a range of about0.05≦Al(4)/Al(6)≦10 and to be 0.5≦p ##EQU2## wherein Ti and X indicategram atoms of titanium and halogen, respectively, Mg indicates gram atomof metallic magnesium or that of Mg in the magnesium compounds and sindicates gram equivalent of alkoxyl group or allyloxyl group in thesilicon compounds. Preferably, the atomic ratio is about0.1≦Al(4)/Al(6)≦5 and 0.8≦p. If the atomic ratio Al(4)/Al(6) is out ofthis range, a result is incurred that the improvement in the powdercharacteristics cannot be achieved, and, if p is too small, the activityof the catalyst becomes low.

The reaction conditions at respective steps are not particularlycritical. However, the addition of components (4) and (6) should beconducted at a temperature no higher than 25° C., preferably no higherthan 15° C. This is especially so if the alpha-olefin is added beforethe magnesium-titanium solution is aged. If the alpha-olefin is addedafter the ageing step, then the temperature during the addition ofcomponent (4) can be higher than 25° C.

The reaction steps may otherwise be conducted at a temperature rangingfrom about -50° to about 300° C., preferably from about 0° to about 200°C., for about 1 to about 6 hours, preferably about 2 to about 4 hours,in an atmosphere of inert gas under normal or applied pressure. It hasbeen found in general that if the reaction temperature for components(4) and (6) is greater than about 25° C., the resulting polymer has asignificant amount of fines.

The solid catalyst ingredient (A) thus obtained may be used as it is.But, it is preferably used in a form of a suspension within the inertorganic solvent after filtering or decanting to remove the unreactedmatters and by-products remained behind and washed several times withthe inert organic solvent. A catalyst from which the inert organicsolvent was removed by isolating after washing and heating under thenormal or reduced pressure can also be used.

In the present invention, as the organometallic compounds of the metalbelonging to Group Ia, IIa, IIb, IIIa or IVa of the Periodic Table whichare the catalyst ingredient (B), organometallic compounds consisting ofmetals such as boron, lithium, magnesium, zinc, tin, aluminum, etc., andorganic groups, and mixtures of such compounds can be mentioned.

As the organic groups described above, alkyl groups can be mentionedtypically. As such alkyl groups, straight or branched chain alkyl groupshaving from 1 to 20 carbon atoms may be used. Specifically, for example,n-butyllithium, diethylmagnesium, diethylzinc, trimethyl- aluminum,triethylalumium, triethylaluminum, tri-i-butylaluminum,tri-n-butylaluminum, tri-n-decylaluminum, tetraethyltin, tetrabutyltinand the like can be mentioned. In particular, the use oftrialkylaluminum is preferable, which has straight or branched chainalkyl groups having 1 to 10 carbon atoms. The most presently preferredcompound is tri-i-butylaluminum.

In addition to the above, as ingredients (B), alkylmetal hydrides whichhave alkyl groups having 1 to 20 carbon atoms can be used. As suchcompounds, diisobutylaluminum hydride, trimethyltin hydride and the likecan be specifically mentioned. Moreover, alkylmetal halides which havealkyl groups having 1 to 20 carbon atoms, for example, ethylaluminumsesquichloride, diethylaluminum chloride and diisobutylaluminumchloride, and alkylmetal alkoxides which have alkoxy groups having 1 to20 carbon atoms, for example, diethylaluminum ethoxide, or the like canbe used.

In addition, organoaluminum compounds obtained through the reaction oftrialkylaluminum or dialkylaluminum hydride which has alkyl groupshaving 1 to 20 carbon atoms with diolefins having 4 to 20 carbon atoms,for example, compounds such as isoprenylaluminum, can also be used.These organometallic compounds may be used independently or incombination of two or more.

As background, the components of (A) and (B) and their reactions aregenerally disclosed in the aforementioned United States patentapplication, except for the presence of the alpha-olefin.

The polymerization of olefins according to the invention can be carriedout under the general reaction conditions used by the so-called Zieglermethod. Namely, polymerization is carried out at a temperature of about20° to 110° C. in a continuous or batch system. The polymerizationpressure is not particularly confined, but the application of pressure,in particular, the use of 1.5 to 50 kg/cm² is suitable. Thepolymerization is carried out in the presence or in the absence of aninert solvent. As polymerization in the absence of inert solvent,so-called vapor phase polymerization, etc. can be mentioned. When thepolymerization is carried out in the presence of an inert solvent, anysuch solvent generally used can be employed. Particularly, alkanes orcycloalkanes having 4 to 20 carbon atoms, for example, isobutane,pentane, hexane, cyclohexane and the like, are suitable.

The polymerization may be conducted through a single polymerizationsystem, but the effect is particularly achieved by the adoption of amultistage polymerization system. The so-called multistagepolymerization system means a system manufacturing through a pluralityof polymerization processes consisting of a process to obtain a polymerof a relatively low molecular weight component and a process to obtainthat of a relatively high molecular weight component. Such multistage orcascade polymerization processes are well known. An example of suchmultistage polymerization is disclosed, for example, in U.S. Pat. No.4,307,209, the disclosure of which is incorporated herein by references.

In such a process, two or more polymerization steps are employed.Typically, in a first step an olefin polymer or copolymer having eithera relatively high or relatively low molecular weight is produced. In asecond step, an olefin polymer or copolymer having a relatively lowmolecular weight or relatively high molecular weight (opposite to thatof the first step) is produced, typically in the presence of the productof the first step. The relatively low molecular weight product may havean intrinsic viscosity of 0.3 to 3, for example, and the high molecularweight component may have an intrinsic viscosity of 1 to 12, forexample, and which is typically at least 1.5 times that of the lowmolecular weight component. The polymerization conditions are selectedso that the weight ratio of the first and second components are within arange to provide a final polymerization product having the desiredproperties. Typically, the weight ratio of the low molecular weightcomponent to the high molecular weight component may be between30-60:40-70. The resulting polymer has a bimodal molecular weightdistribution, and possesses desirable physical properties.

The amount of the catalyst ingredient (A) is to be used is preferablyequivalent to about 0.001 to about 2.5 mmol of titanium atom per literof the solvent or per liter of the reactor, and it can also be raised tohigher concentrations depending on the conditions.

The organometallic compound which is the ingredient (B) is preferablyused at a concentration of about 0.02 to about 50 mmol, preferably about0.2 to about 5 mmol per liter of the solvent or per liter of thereactor.

In the method of preparing polyolefins according to this invention, asolefins to be allowed to polymerize, there can be mentionedalpha-olefins represented by a general formula R--CH═CH₂ (in theformula, R is hydrogen or a straight or branched chain, substituted orunsubstituted alkyl group having 1 to 10, preferably 1 to 8, carbonatoms). Specifically, ethylene, propylene, 1-butene, 1-pentene,4-methyl-1-pentene, 1-octene and the like may be mentioned. Moreover,copolymerization can also be carried out using mixtures of two or moreolefins described above or mixtures of an alpha-olefin with dienes suchas butadiene, isoprene, etc. In such copolymers of ethylene, preferablythe non-ethylene comonomer is present in an amount from about 0.05 to10, more preferably about 0.1 to 5, percent by weight. In particular, itis preferable to use ethylene, mixtures of ethylene with aforementionedan alpha-olefins except ethylene, or mixtures of ethylene with dienes.The presently preferred polymers are homopolymers of ethylene orcopolymers of ethylene and a minor amount of hexene.

In the present invention, the molecular weight of the formed polymer canbe controlled by generally known methods, such as allowing proper amountof hydrogen to exist in the reaction system, etc.

The concentration of hydrogen to control the molecular weight isordinarily about 0.001 to 20 to the concentration of olefin whenexpressed as a ratio, partial pressure of hydrogen/partial pressure ofolefin. For example, with a multistage polymerization, it is selected tobe about 0.01 to 20 in the process of the low molecular weight componentand about 0 to 0.1 in the process of the high molecular weightcomponent. Here, it is necessary to select the molecular weights of boththe low molecular weight component and the high molecular weightcomponent aiming at an average molecular weight consistent with that ofthe object polymer and that the difference of molecular weights betweenthem meets the width of the molecular weight distribution of the objectpolymer.

The present invention provides a polymer with excellent powdercharacteristics. Namely, according to this invention, a polymer withhigh bulk density can be obtained which has also an extremely narrowparticle size distribution, contains only small amounts of fineparticles and further has an average particle diameter of desired size.These are all of great significance industrially. In other words, in thepolymerization process, the formation of the deposits is hindered in thepolymerization reactor and in the processes of separation and drying ofpolymer, the scattering of the fine particles of polymer to outside ofsystem is prevented as well as the separation and the filtration ofpolymer slurry become easy. In addition, the drying efficiency isenhanced due to the improvement in the fluidity. Moreover, at thetransportation stage, the bridging, etc. does not occur in the silo andthe troubles on transference are dissolved. Furthermore, it becomespossible to supply the polymer with constant quality.

A second effect of this invention is to be able to make the distributionof molecular weight narrower. As a result, a polymer having a highimpact strength can be obtained.

EXAMPLES

The following non-limiting examples are given. In the examples andcomparative examples, HLMI/MI, or I22/I2 ratio, means a ratio of highload melt index (HLMI, or I22, in accordance with the condition F inASTM D-1238) to melt index (MI, or I2, in accordance with the conditionE in ASTM D-1238). If the value of HLMI/MI is small, the molecularweight distribution is considered too narrow.

The activity indicates the formation weight (g) of the polymer per 1 gof the solid catalyst ingredient (A) The polyethylene powder obtainedfrom solid catalyst component (A) in a steel autoclave is placed in agrinder prior to particle size analysis. The grinding action is designedto mimic the forces applied to like polyethylene produced in a loopreactor. The distribution of polymer particles is expressed by thedifference in the 84% and 16% cumulative weights divided by the 50%cumulative weight (hereinafter referred to as span) obtained by thegenerally known method from the approximate straight line through thepoints plotting the result of the classification of polymer particleswith sieves on the probability logarithm paper.

Moreover, the average particle diameter is a value read off the particlediameter corresponding to 50% cumulative value in weight with which theabove-mentioned approximate straight line intersects.

EXAMPLE 1

(a) Preparation of Mg-Ti Solution

A 1-liter 4-neck flask equipped with a mechanical stirrer anddistillation apparatus was charged with 68.0 ml (0.20 mole) tetrabutyltitanate, 57.2 g (0.50 mole) magnesium ethylate, 64.1 ml (0.70 mole)n-butanol, 17.7 ml (0.20 mole) 1,4-butanediol, and 0.2 ml water. Themixture was heated under nitrogen to 90° C., after which ethanol beganto distill from the reaction vessel. As the distillation proceeded, thereaction temperature was allowed to rise to 120°-130° C. Afterapproximately 60 ml of distillate had been collected, the mixture washeated at 120° C. for an additional hour. The clear gray solution wasthen diluted with 400 ml hexane and then 100 ml 1-hexene were added. Thesolution was aged for 1 hour at 70° C.

(b) Preparation of Solid Catalyst Component (A)

The Mg-Ti solution was transferred to a graduated 3-liter vesselequipped with a mechanical stirrer and condenser. Diethylaluminumchloride (30% in hexane) (522 ml, 1.0 mole) was added dropwise to theMg-Ti solution at 15° C. Following a 1-hour addition time, the mixturewas aged for 1 hour at 65° C. After the ageing step, 60 ml (1.0 mole)polymethylhydrogen siloxane was added, and the mixture was aged anadditional hour at 65° C. The mixture was then cooled to 15° C, and 1009ml (2.75 mole) iso-butylaluminum dichloride (50% in hexane) was addeddropwise over a 2-hour period. Following the addition, the catalystslurry was heated to 65° C. and stirred for 1.5 hours. Four washingsteps were carried out using the decantation method.

(c) Polymerization of Ethylene

A 2-liter stainless steel autoclave fitted with an electro-magneticstirrer was heated under nitrogen for several hours. A portion of theslurry obtained above which contains 15 mg of the solid catalystcomponent (A) was injected into the autoclave. Subsequently, 1.0 1isobutane was charged to the reactor followed by the addition of 0.18 g(0.91 mmoles) tri-isobutylaluminum. After stabilizing the reactortemperature at 195° F. (90.6° C.), hydrogen was added until the totalpressure was increased by 50 psia (3 5 kg/cm²). Ethylene was then addedto the autoclave and was fed continuously to maintain a total pressureof 398 psia (28.0 kg/cm²). The polymerization was conducted for 1.5hours at 195° F. (90.6° C.). Following completion of the polymerization,the ethylene flow as terminated, and the solvent and unreacted gaseswere purged from the reactor. Polyethylene powder was removed from theautoclave and dried at 50° C.

A total weight of 231 g polyethylene having a melt index of 0.57 g/10min and an HLMI/MI ratio of 35.0 was produced. The formation weight per1 gram of the solid catalyst ingredient (A) (hereinafter referred to asactivity) corresponded to 15400 g/g. Moreover, the average particlediameter was 519 microns, the span was 0.65 and the amount of fineparticles below 210 microns was 4.9 wt. %.

COMPARATIVE EXAMPLES 2-5

Using the procedure described in Example 1 (a), the Mg-Ti solution wasdiluted with 500 ml hexane, without any alpha-olefin additive. Theresulting Mg-Ti solution was further treated as described in Example 1(b).

Using 0.18 g of tri-isobutylaluminum and 15 mg of the solid catalystcomponent (A) obtained by the above-mentioned method, ethylene waspolymerized under the similar conditions to those in Example 1 (c), asset forth in Table 1 below. The properties of the resulting polymer arealso shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                  Example                                                                       2     3         4       5                                           ______________________________________                                        Olefin      none    none      none  none                                      Reaction     195     210       195   195                                      Temp., °F.                                                             [°C.]                                                                              [90.6]  [98.9]    [90.6]                                                                              [90.6]                                    Activity,   16400   17867     16400 16000                                     g/g cat.                                                                      I2, g/10 min                                                                              0.15    1.6       5.22  0.3                                       I22, g/10 min                                                                             5.03    51.96     161.46                                                                              10.18                                     I22/I2 Ratio                                                                              33.5    32.5      30.9  33.9                                      APS, microns                                                                               374     407       386   418                                      Span        0.8     0.69      0.78  0.73                                      Fines, %    7.8     5.4       7.4   6.1                                       ______________________________________                                         Notes:                                                                        APS = Average particle size                                                   Fines = Particles less than 210 microns                                  

EXAMPLES 6-10

Example 1 was repeated under the conditions set forth in Table 2 below.The properties of the resulting polymer are also set forth in the table.

                  TABLE 2                                                         ______________________________________                                               Example                                                                       6      7        8        9      10                                     ______________________________________                                        Olefin   Hx       Hx       Hx     Hx     Hx                                   Reaction  195      210      211    195    195                                 Temp., °F.                                                             [°C.]                                                                           [90.6]   [98.9]   [99.4] [90.6] [90.6]                               Activity,                                                                              18867    14400    14000  15000  16333                                g/g cat.                                                                      I2, g/10 min                                                                           0.56     0.98     0.61   0.55   0.69                                 I22, g/10 min                                                                          23.98    34.26    22.37  20.41  23.3                                 I22/I2 Ratio                                                                           42.8     35.0     36.7   37.1   33.8                                 APS, microns                                                                            490      525      494    522    493                                 Span     0.57     0.55     0.56   0.59   0.66                                 Fines, % 3.9      1.8      3.1    2.3    2.8                                  ______________________________________                                         Notes                                                                         Hx = 1hexene                                                             

EXAMPLES 11-16

Example 1 was repeated using 1-octene and 1-tetradecene as thealpha-olefin, under the conditions set forth in Table 3 below. Theproperties of the resulting polymer are also set forth in the table.

                  TABLE 3                                                         ______________________________________                                               Example                                                                       11    12      13      14    15    16                                   ______________________________________                                        Olefin   Oc      Oc      Oc    Oc    Td    Td                                 Reaction  193     210     195   210   195   195                               Temp., °F.                                                             [°C.]                                                                           [89.4]  [98.6]  [90.6]                                                                              [98.9]                                                                              [90.6]                                                                              [90.6]                             Activity,                                                                              14667   13467   20400 14467 17933 15867                              g/g cat.                                                                      I2, g/10 min                                                                           0.97    1.63    1.14  2.87  0.15  1.27                               I22, g/10 min                                                                          39.8    53.12   43.06 108.96                                                                              7.37  45.75                              I22/I2 Ratio                                                                           41.0    32.6    37.8  38.0  49.1  36.0                               APS, microns                                                                            372     476     495   501   468   475                               Span     0.74    0.53    0.56  0.49  0.57  0.63                               Fines, % 5.5     2.5     3.5   1.2   5.3   3.5                                ______________________________________                                         Notes                                                                         Oc = 1octene                                                                  Td = 1tetradecene                                                        

The average particle size, fines, and span data from ComparativeExamples 2-5 and Examples 1 and 6-14 were averaged. According to theF-distribution, the differences in the data averages between the hexenemodified catalysts and the comparative catalysts were significant at the99 percent certainty level. In addition, the differences in the finesand span averages were significant at the 95 percent certainty level forthe octene modified catalysts.

From the above examples, it can be seen that an improvement in particlesize and the amount of fines is achieved when using the alpha-olefins ofthis invention.

In this disclosure, when refering to the groups of the Periodic Table,reference is made to the groups as defined in the Periodic Table of TheElements appearing in Lange's Handbook of Chemistry, McGraw-Hill BookCompany, 13th Edition (1985). It is noted that the nomenclature of thegroups of this invention is somewhat different than that appearing inthe aforementioned Japanese published patent application 60-262802.

It can be seen that the present invention provides an improved catalystsystem for olefin polymers. The resulting free-flowing polyolefin ischaracterized by a large average particle size and small amount of fineparticles. At the same time, the desirable properties of narrowmolecular weight distribution and high catalyst activity are retained.

What is claimed is:
 1. A catalyst useful for preparing an olefinpolymer, said catalyst comprising a combination of ingredients (A) and(B), wherein ingredient (A) is a solid catalyst by the reaction of ahomogengous solution comprising (1), (2) and (3) below:(1) at least oneof a mixture of (a) metallic magnesium and/or an oxygen-containingorganic compound of magnesium and (b) the combination of at least onemonohydroxylated organic compound and at least one polyhydroxylatedorganic compound in which each hydroxyl group is separated by at leastfour atoms in the molecule; and (2) at least one oxygen-containingorganic compound of titanium wherein the oxygen is directly attached tothe titanium; and (3) at least one alpha-olefin having at least 4 carbonatoms; and in which said solution of (1), (2) and (3) is reacted insequence with (4) at least one first halogenated aluminum compoundhaving the formula R_(n) ² AlY_(3-n), wherein R² represents ahydrocarbon having 1 to 20 carbon atoms, Y is a halogen atom, and 1≦n<3;then (5) at least one silicon compound selected from the groupconsisting of polysiloxanes and silanes, and mixtures thereof; then (6)at least one second halogenated aluminum compound selected fromcompounds having the formula R_(Z) ⁶ AlX_(3-Z), wherein R⁶ represents ahydrocarbon having 1 to 20 carbon atoms, Y is a halogen and 1≦z<3, andingredient B is an organometallic compound containing a metal from GroupIa, IIa, IIb, IIIa or IVa of the Periodic Table.
 2. The catalyst ofclaim 1, wherein said component (3) is an alpha-mono-olefin.
 3. Thecatalyst of claim 2, wherein said alpha-mono-olefin has 5 to 18 carbonatoms.
 4. The catalyst of claim 3, wherein said alpha-mono- olefin isselected from the group consisting of 1-pentene, 1-hexene, 1-octene,1-decene, 1-dodecene, 1-tetradecene, 3-methyl butene and 4-methylpentene, and mixtures thereof.
 5. The catalyst of claim 1, wherein saidcomponent (3) is a diene or polyene.
 6. The catalyst of claim 5, whereinsaid component (3) is selected from the group consisting of1,4-hexadiene, 1,5,9-decatriene, 2-methyl-1,7-octadiene, 1,6-octadiene,1,9-decadiene, 1,13-tetradecadiene and 2,6-dimethyl-1,5- heptadiene, andmixtures thereof.
 7. The catalyst of claim 1, wherein saidpolyhydroxylated organic compound is a dihydroxylated organic compound.8. The catalyst of claim 7, wherein said dihydroxylated organic compoundis a straight or branched chain diol.
 9. The catalyst of claim 7,wherein said dihydroxylated organic compound is 1,4-butanediol and saidmonohydroxylated organic compound is n-butanol.
 10. The catalyst ofclaim 1, wherein said polyhydroxylated organic compound is selected fromthe group consisting of 1,4-butanediol, 1,6-hexanediol,2,5-dimethyl-2,5-hexanediol, diethylene glycol, 2,2'-thiodiethanol,N-ethyldiethanolamine, silanol terminated polydimethylsiloxanes andmixtures thereof.
 11. The catalyst of claim 1, wherein saidmonohydroxyalted organic compound is selected from the group consistingof alcohols, organosilanols and phenols, and mixtures thereof.
 12. Thecatalyst of claim 11, wherein said monohydroxylated organic compound isselected from the group consisting of straight or branched chainaliphatic alcohols, alicyclic alcohols and aromatic alcohols having 1 to18 carbon atoms, and mixtures thereof.